From: David (Ming Qiang) Wu Date: Wed, 14 May 2025 22:50:15 +0000 (-0400) Subject: drm/amdgpu/vcn1: read back register after written X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=0ef2803173f180fe31b5083b1dcf0f8fa6e5608f;p=linux-2.6-microblaze.git drm/amdgpu/vcn1: read back register after written V3: drop changes where readbacks have implemented. This patch set is to add readbacks only. V2: use common register UVD_STATUS for readback (standard PCI MMIO behavior, i.e. readback post all writes to let the writes hit the hardware) add readback in ..._stop() for more coverage. Similar to the changes made for VCN v4.0.5 where readback to post the writes to avoid race with the doorbell, the addition of register readback support in other VCN versions is intended to prevent potential race conditions, even though such issues have not been observed yet. This change ensures consistency across different VCN variants and helps avoid similar issues. The overhead introduced is negligible. Reviewed-by: Ruijing Dong Signed-off-by: David (Ming Qiang) Wu Signed-off-by: Alex Deucher --- diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c index 21b57c29bf7d..c74947705d77 100644 --- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c @@ -1009,6 +1009,11 @@ static int vcn_v1_0_start_spg_mode(struct amdgpu_vcn_inst *vinst) jpeg_v1_0_start(adev, 0); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(UVD, 0, mmUVD_STATUS); + return 0; } @@ -1154,6 +1159,11 @@ static int vcn_v1_0_start_dpg_mode(struct amdgpu_vcn_inst *vinst) jpeg_v1_0_start(adev, 1); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(UVD, 0, mmUVD_STATUS); + return 0; } @@ -1216,6 +1226,12 @@ static int vcn_v1_0_stop_spg_mode(struct amdgpu_vcn_inst *vinst) vcn_v1_0_enable_clock_gating(vinst); vcn_1_0_enable_static_power_gating(vinst); + + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(UVD, 0, mmUVD_STATUS); + return 0; } @@ -1250,6 +1266,11 @@ static int vcn_v1_0_stop_dpg_mode(struct amdgpu_vcn_inst *vinst) WREG32_P(SOC15_REG_OFFSET(UVD, 0, mmUVD_POWER_STATUS), 0, ~UVD_POWER_STATUS__UVD_PG_MODE_MASK); + /* Keeping one read-back to ensure all register writes are done, + * otherwise it may introduce race conditions. + */ + RREG32_SOC15(UVD, 0, mmUVD_STATUS); + return 0; }